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What are the clinical signs of salmonella in adult cattle?

salmonella infection causes enteritis and septicaemia often with abortion if infection occurs in late pregnancy or shedding of the causative organism into milk. S dublin can cause abortion with no signs of enteritis/septicaemia. most severe in stressed groups of animals eg newly calved dairy cows, cows in poor body condition, cows in late pregnancy etc. Main clinical signs include acute enteritis, pyrexia, acute milk drop if lactating, depression, septicaemia, abortion followed by septic metritis in some cases.


How is salmonellosis diagnosed?

Easily isolated from faeces. lab will inform defra who will inform public health.


What are the main differential diagnosis when considering salmonella?

BVD, mucosal disease, winter dysentery, indigestion


What is the treatment of salmonellosis?

Isolate affected animals if possible to limit spread. Systemic antibiotics may prolong excretion if used at insufficient doses. Efficacy dubious in adult cattle. prompt treatment of calves during outbreak may prevent septicaemia and sequelae. Supportive treatment may also be needed - NSAIDS, oral iv fluids, nursing. Recovery can be prolonged.


How is the salmonella vaccine used?

two doses 3-4 weeks apart to stimulate immunity, vaccinating in late pregnancy will improve colostral antibody levels for calves. May be worthwhile using to help protect high risk groups of cattle on farm following outbreak.


How can salmonella be prevented on farm?

Avoid introducing infected animals, quarantine introduced stock for 4 weeks, source new stock form other farms not dealers, avoid shared bulls and communal grazing, use dedicated isolation boxes, clean and disinfecte buildings between occupancies, maintain good fences to prevent access of neighbouring stock, protect feed stores from vermin, including birds, avoid contamination of water sources, only spread slurry on arable land, leave grazing land at least 3 weeks after spreading slurry.


What is the suspected cause of winter dysentery?

Bovine coronavirus - has been demonstrated in the faeces and colonic epithelium of affected cattle and the disease has been reproduced experimentally in susceptible adult cows by exposure to coronavirus isolated from calves.


What are the clinical signs of winter dysentery?

acute explosive watery diarrhoea, often dark brown with flecks of blood and malodorous. usually not pyrexic, partial anorexia, depression and milk drop if lactating, cows may show colic symptoms. may be mild respiratory signs, coughing, naso lacrimal discharge. Quickly spreads in herd but outbreak over within 2 weeks.


What is the cause of johnes disease?

a chronic granulomatous enteritis of adult ruminants caused by mycobacterium avium subspecies paratuberculosis.


How is Johnes disease transmitted?

By ingestion of the organism in faeces from infected animals, contaminating food, water or teats. infection mainly occurs in neonatal animals up to a few months old but occasionally older animals also become infected.


When does clinical disease with johnes show symptoms?

usually a long incubation period and clinical disease is not usually apparent until 3-5 years of age although younger cases are possible with a high challenge.


What host factors encourage disease?

Parturition, transport, poor nutrition, concurrent disease, breed susceptibilities.


What is the pathogenesis of Johnes disease?

After ingestion the organism localises in the ileum and gut associated LNs. it is phagocytosed by macrophages and may multiply intracellularly. Depending on the host pathogen balance the animal may become resistant, intermediate (infection partially controlled, shedder) or clinical.


What are the clinical signs of johnes?

usually appear age 2-6 years with onset often linked to recent calving. progressive weight loss and emaciation are the major signs and may also have submandibular oedema and coat depigmentation, fall in milk yield. there is no fever or toxaemia. rumenal activity is normal. Cattle have soft thick diarrhoea with no blood mucus and tenesmus.


Which faecal examination tests can be used to diagnose Johnes?

1- microscopic examination for clumps of acid fast organisms with a ZN stain. Detects heavy shedders but may miss intermittent light shedders.
2- culture of faeces on mycobactin containing media. Grows v slowly up to 3 months.
3- PCR techniques to detect DNA small quantities in faeces,


Which serological tests can be used to diagnose Johnes?

Complement fixation test - not good specificity/sensitivity in subclinical cases.
Agar gel immunodiffusion test - poor at detecting subclinical.
ELISA - best option though still relatively low sensitivity in subclinical animals.


How can Johnes be controlled?

Control is difficult because of the long incubation period, shedding by subclinically infected animals and the imperfect diagnostic techniques. eradication requires a substantial commitment. Serology or faecal pcr may be done every 6-12 months with slaughter of positive cases. Two consecutive negative whole herd tests may indicate eradication. Minimise faecal contamination of food, water and pasture by raising feed and water troughs, strip grazing, use of piped rather than pond water, avoid spreading yard manure on pasture, maintain good hygiene, separate new born calves from dams at birth and rear by bucket.


What are the clinical signs of Johnes in sheep?

Progressive weight loss, sometimes with wool shedding. The faeces usually remains as firm pellets but soft faeces and diarrhoea may deevelop in some advanced clinical case. As with cattle the disease is fatal once signs occur.


How long is the gestation in a cow?

280-285 days.


What type of placenta do cows have?

cotyledonary syndesmochorial. Placental cotyledons attach to maternal caruncles to form placentomes. 120 in total. Arranged in 4 longitudnal rows in each horn.


When does the foetus begin to lie in anterior presentation?

at the end of 6 months, the length of the foetus is > the width of the amnion so that foetus lies in the anterior presentation from then onwards.


What is the source of progesterone in pregnancy?

Until day 150 is the CL. Beyond day 150 the CL isnt the sole source of progesterone which is produced by t he ovarian stroma, the placenta and the adrenals.


What can be used to terminate a pregnancy?

Prostaglandin alone up to 150 days,
Beyond day 150+ need combination of Progesterone and corticosteroid injection.


What can you induce parturition with in a cow?

close to gestation - corticosteroid or PGF2a - parturition within 48-72 hours. Cow between 250-270 days of gestation - PGF2a alone will not reliable cause abortion at this stage of pregnancy, best option is a combination of dexamethasone and PGF2a. abortion should occur in 5 days.


How long should you wait after a misalliance pregnancy to terminate?

atleast 7 days to ensure responsive CL is present.


When are most pregnancies lost?

Early embryonic mortality before day 19. When loss occurs before day 19 then maternal recognition of pregnancy does not occur and the cow will then return to oestrus 18-24 days later, therefore no abnormal interoestrus interval will be observed.


By what point must the cow recognise the pregnancy to prevent luteolysis?

day 16


How does the cow recognise the pregnancy?

Interferon - tau is secreted from the blastocyst >15mm diameter normally by day 15 until around day 20.


How does interferon - tau work?

It has anti luteolytic properties as it inhibits oxytocin receptor expression in the endometrium which prevents prostaglandin production by the endometrium and prevents luteolysis.


When does mummification occur?

Mummification can only take place when the foetus dies well before the time of expulsion or removal. There is a foetal death in utero, persistence of the CL, cervix remains closed and uterine contractions are absent. Either papyraceous (all fluids reabsorbed) or haematic (blood degenerates into a viscous brown material)